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Patient information · Urgent care and cardiology

Fainting and blackouts
the ordinary kind, and the kind that needs investigating

Most faints are harmless: a brief drop in blood pressure with clear triggers and clear warning signs, followed by rapid full recovery. A minority point to a heart problem, and those are identified by the circumstances rather than by how dramatic the faint looked.

The ordinary faint

A simple faint happens when blood pressure and heart rate drop briefly, reducing blood flow to the brain. Common triggers are standing for a long time, heat, a hot bath, pain, the sight of blood, having blood taken, coughing, straining, dehydration, missing meals, or a sudden fright.

There is almost always a warning: feeling light-headed or hot, sweating, nausea, ringing in the ears, and vision closing in from the edges. Recovery is quick and complete within a minute or two, though feeling washed out for a few hours afterwards is normal. Brief twitching as someone faints is common and does not mean it was a seizure.

Stopping a faint before it happens

If you feel one coming on, act at once rather than trying to carry on.

1. Lie down immediately and raise your legs. If you cannot lie down, sit and put your head between your knees.
2. Cross your legs and tense them hard, squeezing your thighs and buttocks together. This pushes blood back towards the heart and often aborts the faint.
3. Grip one hand with the other and pull apart hard, tensing your arms at the same time.
4. Stay down until the feeling has fully passed, then get up slowly in stages.

If someone else faints

• Lay them flat and raise their legs above heart level.
• Do not sit them up or prop them in a chair, and never try to walk them to fresh air — this is the commonest mistake and it prolongs the faint.
• Loosen tight clothing at the neck and make space around them.
• If they do not regain consciousness within a minute, put them in the recovery position and call 999.
• When they come round, let them lie still for several minutes before sitting, then before standing.
• Do not give anything to eat or drink until they are fully alert.

Reducing how often it happens

• Drink enough fluid through the day; dehydration is the most common contributor.
• Do not skip meals.
• Stand up in stages — sit on the edge of the bed for a moment before standing.
• Avoid standing still for long periods; if you must, shift your weight and flex your calves.
• Be careful with hot baths, saunas and alcohol.
• Tell the person taking your blood that you faint — they will lie you down.

Driving

There are legal rules about driving after a blackout, and they depend on the cause, whether there was warning, and whether you hold an ordinary or a vocational licence. A single simple faint with clear triggers and warning usually carries no restriction. An unexplained blackout does. You must inform the DVLA in certain circumstances and it is your responsibility to do so — we will advise you which category you fall into and can put it in writing.

What assessment involves

Usually an account of exactly what happened before, during and after — which is the most valuable part — along with an examination, lying and standing blood pressure, an ECG, and blood tests. Where the story or the ECG raises questions, a heart rhythm monitor, an echocardiogram or a cardiology opinion may follow.

Related: Cardiology · Echocardiography · Private GP · Driver medicals · All patient leaflets